Overall, on a scale from one to ten, I would give WatchGuard a rating of nine. I would recommend WatchGuard or something from FortiGate. These two solutions are pretty similar and very good in terms of quality and functionality. I have personally used both of them and they're great.
When we implement a new product such as this, we start with a PoC. We ask our vendor to provide a demonstration and then we use it in our environment. This allows us to test each of our scenarios. My advice to others is to follow this approach whenever they want to use a product. Do the testing before they buy it. Every product has it's weaknesses. Just because it benefits one company, doesn't mean that it benefits another. This is why testing is important. I would rate this solution an eight out of ten.
We're a WatchGuard Silver Partner. I'm not sure which version of the solution our organization is currently using. Our company is quite small, but we service medium-sized organizations and have a large number of clients. I'd rate the solution seven out of ten.